An electric space heater is used to heat a room.
The dimensions of the room are 4.0 m×5.5 m×2.5 m4.0\text{ m} \times 5.5\text{ m} \times 2.5\text{ m}4.0 m×5.5 m×2.5 m. The density of air is 1.2 kg/m3. Show that the mass of air in the room is 66 kg.
The power of the heater is 1200 W. The specific heat capacity of air is 1000 J/(kg∘C)1000\text{ J/(kg}^\circ\text{C)}1000 J/(kg∘C). Calculate the time taken to increase the temperature of the air in the room from 15.0∘C15.0^\circ\text{C}15.0∘C to 21.0∘C21.0^\circ\text{C}21.0∘C.
Suggest one reason why the actual time taken to increase the temperature of the room's air would be greater than the time calculated in (a)(ii).
The walls of the room are insulated with cavity-wall insulation (foam injected between two brick layers). State the main methods of thermal energy transfer through the walls that are reduced by this insulation.
119 exam-style questions on CIE IGCSE Physics 2.2.2a Internal energy and temperature. Each one has a worked solution and a mark scheme showing where the marks go.